OpenAPIToolset automatically converts camelCase to snake_case with no option to disable

Is your feature request related to a problem? Please describe.
ADK's OpenAPIToolset automatically converts camelCase to snake_case when generating tool parameters, and there doesn't appear to be a built-in option to disable this. This is a problem when calling APIs which expect camelCase property names in the request body.

For example, an OpenAPI spec with sessionInfo gets converted to session_info in the actual API call, causing the target API to reject the request.

Describe the solution you'd like
It would be good to be able to flag parameters in the OpenAPI spec to preserve their original casing. For example, a vendor extension like:

sessionInfo:
  type: object
  x-adk-preserve-case: true
  properties:
    session:
      type: string

Or a global option in the OpenAPIToolset constructor:

toolset = OpenAPIToolset(
    spec_str=spec_content,
    spec_str_type="yaml",
    preserve_property_names=True,  # Skip snake_case conversion
)

Describe alternatives you've considered

Modifying the target API to accept both session_info and sessionInfo - works but requires changes to every API endpoint
Creating a custom FunctionTool wrapper instead of using OpenAPIToolset - bypasses the conversion but loses the benefits of automatic OpenAPI parsing
Using snake_case in the OpenAPI spec - but this misrepresents the actual API contract
Additional context
The conversion happens in _sanitize_schema_formats_for_gemini in _gemini_schema_util.py at line 154:

field_name = _to_snake_case(field_name)
This converts all OpenAPI schema field names to snake_case before passing them to Gemini. While rest_api_tool.py does store original_name for parameters, the schema transformation happens before this mapping can preserve the original casing in the request body.

@adrianthompson-lh

@adrianthompson-lh Thanks for the update. The request is currently being reviewed, and I will let you know if anything further is needed. Thank you for your understanding.

feat(tools): add preserve_property_names option to OpenAPIToolset

Opened a PR for this: #4505

Added a preserve_property_names parameter to OpenAPIToolset that keeps original property names from the OpenAPI spec instead of converting them to snake_case. Backward compatible — defaults to False.

feat(tools): add preserve_property_names option to OpenAPIToolset

Fixed on main via #4505 (commit 078b516): OpenAPIToolset now has a preserve_property_names option to keep the original spec names instead of forcing snake_case. Closing as fixed.

Navigation Menu

Repository navigation

OpenAPIToolset automatically converts camelCase to snake_case with no option to disable #4166

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

OpenAPIToolset automatically converts camelCase to snake_case with no option to disable #4166

Description

Activity

klateefa commented on Feb 11, 2026

yuvrajangadsingh commented on Feb 16, 2026

GWeale commented on Jun 17, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions